The present disclosure is generally directed to ultrasonic surgical blades employed in ultrasonic instruments. At present, ultrasonic instruments are used in open as well as minimally invasive surgical procedures, including endoscopic and laparoscopic surgical procedures where an end-effector portion of the ultrasonic instrument is passed through a trocar to reach the surgical site. Due, in part, to the rising popularity of minimally invasive surgical procedures, ultrasonic instruments are increasingly being used for the safe and effective treatment of many medical conditions. The operation of instruments employing an ultrasonic transducer in this context is well known in the art and it will not be repeated herein for the sake of conciseness and brevity. Stated briefly, an ultrasonic transducer excited by an electrical generator produces mechanical vibrations at ultrasonic frequencies, which are transmitted longitudinally through a transmission component or waveguide to an end-effector. The mechanical vibrations induce longitudinal, transverse, or torsional vibratory movement to the end-effector relative to the transmission component. The vibratory movement of the end-effector generates localized heat within adjacent tissue, facilitating both cutting and coagulating of tissue at the same time. Accordingly, the ultrasonic vibrations, when transmitted to organic tissue at suitable energy levels using a suitable end-effector, may be used to cut, dissect, separate, lift, transect, elevate, coagulate or cauterize tissue, or to separate or scrape muscle tissue away from bone with or without the assistance of a clamping assembly.
It is generally accepted that ultrasonic instruments, and particularly ultrasonic instruments comprising contact ultrasonic elements, provide certain advantages over other surgical instruments. Among these advantages is that the ultrasonic mechanical vibrations can cut and coagulate tissue at the same time using relatively lower temperatures than conventional cutting and cauterizing surgical instruments. The nature of ultrasonic instruments lend themselves to multiple applications and a variety of end-effectors may be designed to perform numerous functions.
Ultrasonic instruments may be classified into single-element end-effector devices and multiple-element end-effector devices. Single-element end-effector devices include instruments such as blades, scalpels, hooks, and/or ball coagulators. Although generally, these types of end-effectors are formed of solid materials suitable for propagating ultrasonic waves, there also exist end-effectors with a hollow core to deliver a fluid stream or provide a suction channel. Multiple-element end-effectors include the single-element end-effector—blade—operatively coupled to a clamping mechanism for pressing or clamping tissue between the blade and the clamping mechanism. Multiple-element end-effectors include clamping scalpels, clamping coagulators or any combination of a clamping mechanism and a single-element end-effector. Clamping end-effectors are particularly useful when a substantial amount of pressure is necessary to effectively couple ultrasonic energy from the blade to the tissue. Clamping end-effectors apply a compressive or biasing force to the tissue to promote faster cutting and coagulation of tissue, particularly loose and unsupported tissue.
With this general background in mind, it should be noted that surgical environments where ultrasonic instruments are employed can be particularly harsh due to the mechanical vibratory forces applied to the end-effector, the resulting thermal effects, and the general caustic conditions present at the surgical site. For example, in use, the end-effector comes into contact with surgical matter, which includes coagulants, proteins, blood, tissue particles, and other constituent fluids. Over time, the surgical matter tends to desiccate and adhere to the outer (e.g., external) surface of the end-effector. This buildup of surgical matter tends to reduce the performance of the end-effector by reducing the ability of the end-effector to cut and/or coagulate tissue and increasing the impedance at the end-effector/tissue interface. To compensate for the increase in interface impedance, the generator supplies increasing amounts of power to the end-effector to continue transecting tissue until the power delivered by the generator exceeds a predetermined threshold at which time the generator shuts down or goes into “lockout.” Lockout is a condition where the impedance of the end-effector is so high that the generator is unable to provide meaningful amounts of power to the tissue. Generator lockout is an undesirable result that occurs when the generator is unable to supply adequate power to the end-effector to complete a transection under the increased interface impedance condition. The completion of a transection is indicated to the user by the visual separation of the tissue from the device end-effector. When the generator goes into lockout, the surgical procedure is interrupted. Therefore, generator lockout results in increased cutting and transection times, or worse, down time during the surgical procedure.
Accordingly, there is a need for an end-effector with a suitable coating or suitable combination of a coating and a surface treatment to protect the end-effector from harsh surgical environments. In this regard, the suitable coating or suitable combination of a coating and a surface treatment prevents or minimizes buildup of surgical matter on the outer surface of the end-effector, minimizes generator lockout, minimizes power draw, improves pad wear in clamping type end-effectors, and improves the thermal characteristics of the end-effector. There is also needed a process of applying one or more suitable coatings to an outer surface of an end-effector to enable the adhesion of the one or more coatings to the outer surface of the end-effector.